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AP_Math: added smaller footprint crc32

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This commit is contained in:
Andrew Tridgell 2019-10-27 22:50:01 +11:00
parent 5898dc757c
commit ff2cfbaafb
2 changed files with 17 additions and 0 deletions
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16
libraries/AP_Math/crc.cpp
View File

@ -167,6 +167,7 @@ static const uint32_t crc32_tab[] = {
0xb40bbe37, 0xc30c8ea1, 0x5a05df1b, 0x2d02ef8d
};
uint32_t crc_crc32(uint32_t crc, const uint8_t *buf, uint32_t size)
{
for (uint32_t i=0; i<size; i++) {
@ -176,6 +177,21 @@ uint32_t crc_crc32(uint32_t crc, const uint8_t *buf, uint32_t size)
return crc;
}
// smaller (and slower) crc32 for bootloader
uint32_t crc32_small(uint32_t crc, const uint8_t *buf, uint32_t size)
{
while (size--) {
const uint8_t byte = *buf++;
crc ^= byte;
for (uint8_t i=0; i<8; i++) {
const uint32_t mask = -(crc & 1);
crc >>= 1;
crc ^= (0xEDB88320 & mask);
}
}
return crc;
}
/*
* Copyright (C) 2010 Swift Navigation Inc.
* Contact: Fergus Noble <fergus@swift-nav.com>

1
libraries/AP_Math/crc.h
View File

@ -22,6 +22,7 @@ uint8_t crc_crc8(const uint8_t *p, uint8_t len);
uint16_t crc_xmodem_update(uint16_t crc, uint8_t data);
uint16_t crc_xmodem(const uint8_t *data, uint16_t len);
uint32_t crc_crc32(uint32_t crc, const uint8_t *buf, uint32_t size);
uint32_t crc32_small(uint32_t crc, const uint8_t *buf, uint32_t size);
// Copyright (C) 2010 Swift Navigation Inc.
// Contact: Fergus Noble <fergus@swift-nav.com>